The present invention relates to a method for applying flat punched elements to the surface of a carrier material, in particular signature stripes made of paper to the cover films of cards, the elements being present in multiple copies on a sheet.
Due to their high protection from forgery, identity cards and entitlement cards are preferred in which the data to be protected from manipulation are applied to a "card inlay" laminated between two transparent cover films. To increase its protection from forgery, the card inlay bears a high-security print and other authenticity features such as watermarks, security threads, etc.
The cards are produced by known methods predominantly in a sheet form. For financial reasons one uses sheets which are as large as possible and divided into a plurality of individual card-sized copies. The arrangement of the copies is preferably identical on all sheets. The sheets of paper and plastic required for the subsequent card compound are prepared separately and superimposed in exact register prior to the lamination process. If possible, this process is performed automatically using sheet feeders or similar machines. The layers of paper and plastic are bonded together in a usual laminating press by the action of pressure and heat. The individual cards are thereafter punched out of the sheet material.
The individual card often has one or more layers covering only part of the total card surface. A typical example of this is a signature stripe extending across the card surface as a strip of paper about one centimeter wide. As only part of the surface is covered, the areas not required are punched out of the corresponding sheet and removed. To prevent the sheet from disintegrating completely into single elements during punching, the punching pattern is such that the elements remain interconnected by bridges. As a result one obtains a "grid sheet".
However, the punched openings have the unpleasant property of reducing the inherent stability of the sheet. The smaller the basis weight and the larger the sheet, the greater is the reduction of stability. Due to the low inherent stability, the grid sheet tends to warp or tear during handling and transport. A large punched surface increases the problems of handling the grid sheet, so that it can finally only be processed into a card compound by difficult manual work. This is particularly disadvantageous in the production of large piece numbers, since the processing of the grid sheets is a bottleneck in the production process that can hardly be economized.
Furthermore, grid sheets can always be used only when the individual elements extend at least to one edge of the card. It is not possible to use grid sheets to produce cards with "edgeless" elements located like islands on the card surface with no connection to the edge.
The invention is based on the problem of stating an automatic, and thus efficient, method making it possible to apply flat elements to the surface of a carrier material precisely and without error. The method and apparatus are also intended to be capable of integration in the existing production equipment that is found in printing companies.
A further problem is to design the automatic method in such a way that it is suitable for applying both edgeless and "edge-toughing" elements.